random loud clunking noise from engine/tranny area
Thread Starter
Instructor
Joined: May 2009
Posts: 240
Likes: 0
From: Norman Oklahoma
random loud clunking noise from engine/tranny area
I have this loud clunking noise coming from the front of the car and it always happens right when I start it but then it will stop and happen again randomly. There's no pattern to it and its not continuous, just random when it wants to. The most recent thing I did was install headers and it didn't make the noise ever before the headers were installed. The car has pretty much been sitting since May when I got in a wreck, not my fault, and I've almost made it road worthy again working on it since then. The motor has always run great and I have no clue what it is, any ideas?
Race Director
Joined: Dec 1999
Posts: 11,094
Likes: 990
From: Sierra Foothills CA
Since this started after you installed headers, check your headers to see if they're contacting the frame or something else. Until I put a slight dent on a tube on the passenger side header I had an intermittent tapping sound from frame contact, usually on start-up or at idle. Clearances are tight on Vettes and there can be slight variances from car to car, so header fitment can be less than perfect sometimes. 
Drifting
Joined: May 2006
Posts: 1,480
Likes: 2
From: Circleville Ohio
Thread Starter
Instructor
Joined: May 2009
Posts: 240
Likes: 0
From: Norman Oklahoma
I don't think the headers are touching anything. thats why its weird. My dad said maybe the flywheel is cracked. And I did replace one motor mount after my wreck because it was cracked. I'll look again today.
Safety Car
Joined: Mar 2007
Posts: 3,652
Likes: 49
From: Bridgewater nj
Fly wheel is a good place to look. Sometimes if you preload the engine at different rpm you can get it to make a noise. don't forget too check the trans bellhousing bolts and block ears for cracks. common after an accident
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Thread Starter
Instructor
Joined: May 2009
Posts: 240
Likes: 0
From: Norman Oklahoma
I started it in the driveway today and it only made the noise when i started it but then it stopped completely. Then i decided to change gears and put it in reverse, after about two seconds it made the noise again. Then i changed gears again and after a little delay, it again made the noise. So it seems the noise occurs after I change gears and when i start it. I didnt see any flywheel cracks or loose bolts either. This still perplexes me.
Thread Starter
Instructor
Joined: May 2009
Posts: 240
Likes: 0
From: Norman Oklahoma
Had a friend of mine come by today, the guy who built my engine, and i started the car. He knew exactly what it was when he heard it. I guess I switched the 6 and 8 plug wires when I took them off to install the headers. Another stupid mistake by a young kid haha. I sure am glad it was just a simple mistake. I tend to do that sometimes. 
